来自扫描器的用户输入导致try/Catch块中的无限循环，即使在Catch中使用NextLine时也是如此

Question

如果输入了正确的文件名，就没有问题。如果输入了不正确的文件名，无限循环会不断告诉用户输入一个文件名。但它不会等待用户输入文件名。它在无限循环中不断处理第一个错误数据。我在catch块中使用nextLine，它应该清除错误的输入。还尝试了reset（）。我做错了什么？

    public static String reader() {
    boolean fileCorrect = false;

    // Holds the data from the file and is returned.
    StringBuilder fromFile=new StringBuilder("");

    // Loop until the user enter's a filename that the system can find.
    do
    {
        System.out.println("\nEnter filename to open: ");

        //Try with resources to open Scanner object for keyboard input
        try (Scanner keyboard = new Scanner(System.in))
        {
            String fileName = keyboard.next();

            // Trim leading/trailing spaces from filename
            fileName = fileName.trim();

            // The file object opened with try below
            File iFile = new File(fileName);

            //Attempt to open the file, which is automatically closed by try with resources.
            try (Scanner fileInput = new Scanner(iFile))
            {
                //Read the file and append data to the string.
                while (fileInput.hasNextLine())
                {
                    fromFile = fromFile.append(fileInput.nextLine());
                }

                //If we make it this far, no need to loop.
                fileCorrect = true;
            }

            // Catch specific first, a child of IOException. Most likely to happen.
            catch (FileNotFoundException ex)
            {
                System.err.println(ex.getMessage() + ": File not found");
                //ex.printStackTrace();
                keyboard.nextLine();
             }

            // If the scanner somehow closed before data was read.
            catch (IllegalStateException ex)
            {
                System.err.println(ex.getMessage() + ": Error reading from file");
                //ex.printStackTrace();
                keyboard.nextLine();
            }

            // Something else went wrong. Generic catch-all to keep the program from crashing.
            catch (Exception ex)
            {
                System.err.println(ex.getMessage());
                //ex.printStackTrace();
                keyboard.nextLine();
            }

        }

        catch (Exception ex)
        {
            // handle these
        }
    }
    while (!fileCorrect);

Answer 1

将此扫描器键盘=新建扫描器（system.in）；移到do-while循环之前

如果您将其作为try（扫描器键盘=new Scanner(System.In))-它将自动在System.in Scanner上调用close,而Next将不起作用

如果您有正确异常处理程序

catch (Exception ex)
{
      ex.printStackTrace();
}

您将看到消息

java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Scanner.java:907)
    at java.util.Scanner.next(Scanner.java:1416)
    at Main.main(Main.java:38)